Zig-zag filter construction



April 9, 1946. o. H. SCHAAF ZIGZAG FILTER CONSTRUCTION Filed Feb. 1, 1943 J. 3 1. Z I F j I I i. 7 IMF I iT T & w WK m p INVENTOR. OLA/5R h. SCH/14F ATTORNEYS.

Patented Apr. 9, 1946 UNITED STATES PATENT OFFICE ZIG-ZAG FILTER CONSTRUCTION Oliver H. Schaaf, Chagrin Falls, Ohio, assignor to Air-Maze Corporation, Cleveland, Ohio, a corporation of Delaware Application February 1, 1943, Serial No. 474,311

4 Claims.

This invention relates to improvements in fluid treating units for screening small particles from fluid streams, one of the commoner uses of the unit being that of an air filter.

Among the objects of the present invention is the provision of a novel structure of an air filter which is cheap to construct and yet efllcient in operation. It will be understood by those skilled in this art that filters such as this are sometimes used in airplanes where weight and efliciency are the two major factors involved. An object of the present invention therefore is to provide a very efiicient filter utilizing material of very light weight.

Other objects and advantages of the present invention will appear from the accompanying drawing and description and the essential features thereof will be set forth in the appended claims.

In the drawing Fig. l is an elevational view of a simple form of filter constructed according to my invention; Figs. 2 and 3 are enlarged fragmental sectional views taken along the lines 2-2 and 3-4 respectively of Fig. 1; Fig. 4 is a transverse sectional view taken along the line H of Fig. 1; while Fig. 5 is a fragmental view illustrating somewhat diagrammatically how a sheet of screen material is processed to produce the filter of Figs. 1 to 4.

It should be understood at the outset that wherever I have referred to a sheet of screen material, I refer to any material adapted to filter small particles from a stream of air or other fluid passing through the unit whether the same be common woven wire mesh or some other material of equivalent function. For instance, the unit here described might be formed from the cloth covered screen disclosed in the copending United States application of Clarence J. Glanzer, Serial No. 441,067, filed April 30, 1942. But other materials are equally useful for carrying out my invention.

In general the unit here disclosed comprises a sheet III of self-supporting screen material capable of holding any form to which it is bent, the specific form here disclosed being intended to represent woven metallic screen. This sheet is bent to provide a series of zig-zag folds havin parallel ridges and troughs facing alternately in opposite directions, This folded material is suitably held in some sort of frame means, such as that indicated at H, which prevents unfolding of the zig-zag folds by exerting a confining force at right angles to the ridges-for instance, at the right and left hand edges as viewed in Fig. 1.

At the same time, the frame means closes the normally open ends of the zig-zag folds at the top and bottom of Fig. 1 so as to prevent any leakage of unfiltered fluid at these points. It will be understood that the fluid to be filtered passes through the unit through the open front and rear of the frame means H, depositing the particles filtered out on the screen material and within the zig-zag folds. If the minimum weight of screen is to be used, the ridges of the folded material running from top to bottom as viewed in Fig. 1, if plain and uncorrugated, will be insufiiciently rigid to hold the zig-zag folds properly spaced. In other words, in some places the ridges, instead of remaining equally spaced in parallel relation, will sag against each other, preventing the proper entrance of air at such a point. One Of the objects of the present invention, therefore, is to so stiffen this light screen material that it will maintain a substantially uniform parallel relationship between the ridges of the zig-zag folds as illustrated in Fig. 1.

Referring now to Fig. 5, the manner of doing this is illustrated on the portion of sheet I 0 there shown. The flat sheet of screen material I 0 is first run through a crimping or corrugating machine which crimps the entire sheet in the parallel corrugations shown at l2. In one form of the device, these corrugations I 2 are 1 6 inch to 3 5 inch deep and approximately $4 inch apart. The corrugated sheet is then provided with zig-zag folds along the parallel lines indicated at 13 in Fig. 5. This provides the ridges ll best seen in Figs. 1 and 2 facing alternately in opposite directions. Referring to Figs. 1 and 4, it will be noted that the corrugations l2 extend at an angle to the ridges l4 and thus exert quite a remarkable strengthening eifect upon the zig-zag folds. In the broken away portion of Fig. 1, I have attempted to illustrate how these corrugations extend at a gradual incline up one side of the zigzag fold, then across the ridge and down along the other side of the ridge.

I have provided novel and very inexpensive means for insuring a proper spacing of the zigzag folds within the frame means. For this puris assembled the frame means ll squeezes the zig-zag folds together until the laterally spread end portions of the ridges mutually engage each other as indicated at I8. The spreading of the end portions of the ridges is done uniformly by means of a tool so that when the unit is assembled as indicated in Figs. 1 and 3 the ridges ll are uniformly spaced. While the laterally spread portions It need not be placed at the ends of the ridges, I prefer this location because, as illustrated in Fig. 1, such laterally spread portions are overlapped by the frame means which must necessarily cover the edge of the screen at this point to prevent leakage of the fluid stream at the ends of the zig-zag folds. In any case. the laterally spread portions I! must be in alinement along the series of zig-zag folds so that they will mutually engage to perform their spacing function.

Referring to Figs. 1 and 2, it will be noted that air or other fluid passing from front to rear of Fig. 1 or in the direction of the arrow of Fig. 2, will enter between a pair of parallel ridges I4 and will strike a number of the corrugations I! as it travels into the trough of the zig-zag folded arrangement before the fluid succeeds in entirely passing through the screen material. The corrugations I! therefore provide a turbulence of the fluid at this point and also provide deformations in the nature of shelves which more readily catch small particles carried by the fluid stream. In actual use the upper surfaces of the corrugations as indicated at 12a in Fig. 2 become quite dirty, indicating that this action takes place.

It will now be apparent that the combination of the zig-zag folds rendered more rigid by the corrugations I: are cheaply and easily held properly spaced by the laterally spread end portions l5. This permits the use of a light weight screen material which by means of the corrugations has the ridges it held substantially parallel from end to end of the folds, which in Fig. 1 is from top to bottom of the drawing. This permits the air stream to enter to the deepest point of the trough of the zig-zag fold, thus utilizing the entire area of the screen. At the same time the corrugations I! provide the turbulence and dirt retaining shelves previously described and add some twenty per cent additional area over that which would be found if uncorrugated material were provided with zig-zag folds of the same dimensions.

While the filter hereinabove described is satisfactory in every way, in some cases I prefer to reinforce the laterally spread portions of the zig-zag folds so that screen of a relatively pliable nature will be rendered stiffer so as to more readily hold the shape shown in Fig. 3. Such a reinforcement may be provided very inexpensively by folding the marginal edge of the sheet I. along'the line H before crimping. In a filter of small size this fold line would be not" more than one-quarter to one-half inch from the edge of the sheet and parallel thereto. This folded material thus gives a double thickness of screen at the point I! and aids in maintaining the laterally spread end portions of the ridges so as to more accurately space the folds across the face of the filter.

What I claim is:

l. A fluid treating unit comprising a sheet of stiff screen material, said sheet having a series of zig-zag folds therein providing parallel ridges facing alternately in opposite directions, said screen material having spaced portions along said ridges spread laterally, said spread portions of adjacent ridges being in alinement. and means exerting a confining force at right angles to said ridges holding said spread portions in abutting non-overlapping contact, whereby said zig-zag folds are held apart and properly spaced for the flow of fluid between them.

2. A fluid treating unit comprising a sheet of stiff screen material, said sheet having a series of zig-zag folds therein providing parallel ridges facing alternately in opposite directions, the opposite ends of said ridges ending in alinement, said screen material at the ends only of said ridges being spread laterally, and means exerting a confining force at right angles to said ridges holding said spread portions in abutting non-overlapping contact, whereby said zlg-zag folds are held apart and properly spaced for the flow of fluid between them.

3. A fluid treating unit comprising a sheet of stiif screen material, said sheet having a series of zig-zag folds therein providing parallel ridges facing alternately in opposite directions, the opposite ends of said ridges ending in alinement, a frame open front and rear confining said screen material and overlapping the ends of said ridges. said screen material at said ends of said ridges beneath said frame being spread laterally to substantially uniform width for each ridge, and said frame holding said laterally spread ends in abutting non-overlapping contact with each other, whereby said zig-zag folds are held apart and properly spaced over the area exposed within said frame.

4. A unit for filtering gas or air comprising a sheet of stiff screen material, said sheet having a series of zig-zag folds therein providing parallel ridges facing alternately in opposite directions, said screen material having portions of said folds spread laterally toward adjacent folds to form shoulders, and means exerting a confining force on said screen material at right angles to said ridges holding said shoulders in abutting nonoverlapping engagement with adjacent folds, whereby said folds are held properly spaced for the fiow of a gaseous stream through said screen material.

OLIVER H. SCHAAI". 

